The Transport Ministry has ordered the Harbour Department to tighten safety measures after a speedboat collision in a Phuket canal killed two Russian children and injured 19 Russian tourists on Monday.
Deputy Transport Minister Atirat Ratanasate said Harbour Department officials are stepping up their investigation and questioning the captains of both boats involved, to establish the exact cause of the accident.
The captains have been charged with reckless driving causing death and injury.
Their permits have also been revoked.
To avoid such tragedies in future, the department has been ordered to overhaul boat safety measures and ensure that captains and operators meet its standards, Mr Atirat said.
A speed limit of five knots has been imposed on certain canals, most of which are narrow and shallow, he added.
The ministry has also ordered the Phuket Marine Office to conduct safety-awareness courses for boat captains and asked operators to ensure their skippers strictly abide by the law.
"Those who defy the laws will see their helmsman certificates revoked for two years," Mr Atirat warned.
The canal where Monday's fatal accident took place has since been dredged to widen the navigable channel.
The Harbour Department has asked for extra budget next year to hire contractors to dredge other canals in Phuket.
A 12-year-old boy and a nine-year-old girl from Russia were fatally injured when the ALP 111 speedboat on which they were travelling collided with the Panan 5 as it approached Royal Phuket Marina in tambon Ko Kaeo to pick up tourists.
The ALP 111 was insured by South East Insurance, with each passenger covered for 300,000 baht in medical costs, 500,000-baht compensation for the death of a child and 1 million baht for the death of an adult, said Mr Atirat.
The operator of the Panan 5, SeaStar Co, had insurance covering 500,000 baht of medical expenses for each passenger, he added.
The boat also had third-party insurance from Viriyah Co of 15,000 baht for injury.